A consensus regarding which implant-abutment connection type would perform best in the anterior maxilla is lacking.
The purpose of this systematic review was to determine the best implant-abutment ...connection type for anterior single-tooth implants considering esthetics, success, and survival rates.
An electronic search was conducted in MEDLINE, Scopus, Embase, and the Cochrane Library databases to identify clinical studies on single-tooth implants with external and internal hexagon, and/or Morse taper connections. These studies needed to describe at least one of the following outcomes: esthetic score, survival/success rate, or marginal bone loss. The included studies and reports were assessed for bias using the Cochrane risk of bias tool.
Of the 891 articles identified, 29 were selected and analyzed. The most common technical complications were abutment screw loosening and crown-cement loosening, while dehiscence and recession were the most common biological complications. The most frequent complications were dehiscence for external hexagon, crown-cement loosening for the internal hexagon, and ceramic fracture for the Morse taper. Esthetics were favorable for all connections, but the internal hexagon performed better. However, better results for marginal bone loss, success, and survival were found for the Morse taper. The global annual failure rate was 0.90% and 0.2% for Morse taper, 0.3% for external hexagon, and 2.2% for internal hexagon.
This review suggests that Morse taper performs better for survival, success, and marginal bone loss. Internal hexagon performed better for esthetic parameters. Additional controlled studies are needed to provide stronger evidence because the evidence generated in this study was considered low.
Abstract Statement of problem Shade matching natural teeth with ceramic restorations is still an esthetic, clinical challenge. Purpose The purpose of this prospective clinical study was to evaluate ...the influence of color-related factors on the color variation of ceramic restorations based on spectrophotometric analysis. Material and methods Color records were obtained from 11 participants who received 38 lithium disilicate restorations. CIELab color coordinates were measured with a spectrophotometer on the ceramic restoration, tooth (baseline), prepared tooth, and luted ceramics. Color variation (ΔE00 ) was calculated for each variable (luting agent and restoration type, tooth substrate shade, ceramic thickness, and translucency parameters) measured at baseline on the prepared tooth and after cementation of the restorations. Confidence intervals (CI) for the means (95% CI) were calculated, and the ΔE00 values and CIELab individual color coordinates were compared for each pair of variable by using the Student t test or Welch test (α=.05). Results Greater color variation values were observed between measurements obtained on the prepared tooth and luted restoration. The lower ΔE00 values were observed over darker tooth substrate measured at baseline and after luting ( P =.007). Conclusions The 3 conditions evaluated presented clinically visible color differences, highlighting the importance of clinical evaluations on the visual color acceptability limits for restorations, which are usually defined in laboratory studies. The lithium disilicate ceramic showed lower masking ability over darker tooth substrate, whereas the coordinates L*, a*, and b* were cementation-dependent.
Objective To evaluate the effect of restorative strategy (fiber post vs cast post and core), coronal height (0 mm vs 2 mm) and thickness (higher than 1 mm vs lower than 1 mm) on survival rate, ...fracture resistance and stress distribution. Material and Methods Seventy-two bovine teeth were cleaned and allocated in six groups (n = 12). Twenty-four teeth were sectioned at 13 mm length (no remaining coronal structure) and forty-eight were sectioned at 15 mm (2 mm remaining coronal structure). Half of the forty-eight had remaining coronal thickness lower than 1 mm and the other half had thickness higher than 1 mm. All root canals were prepared at 10 mm (luting length), fiber posts were cemented in thirty-six specimens and cast post and core in other thirty-six. All teeth were restored with metallic crowns. Specimens were submitted to 1.5 million cycles (100 N, 45°, 10 Hz at 2 mm below incisal edge) and evaluated at each 500,000 cycles to detect failures. Specimens that survived were submitted to load to fracture test. Bidimensional (Rhinoceros® 4.0) models were obteined survival data submitted to Kaplan-Meier (α=0.05) analysis and load to fracture values submitted to ANOVA and Tukey tests (α=0.05). Results Groups without remaining coronal structure showed survival rates lower than other groups (p=0.001). ANOVA showed higher values of load to fracture for groups with coronal thickness higher than 1 mm (p=0.0043). Finite element analysis showed better stress distribution in groups with remaining coronal structure and restored with fiber post. Conclusion Specimens without remaining coronal structure have lower survival rates. Specimens with remaining structure lower than 1 mm and without coronal structure support the same load to fracture value independently of the restorative strategy.
To evaluate the fracture load and survival rate of weakened and non-weakened roots restored with different intracanal posts.
Eighty teeth (16 mm) were prepared to a length of 10 mm with a custom ...drill. Fifty roots were weakened with a tapered diamond drill, and 30 roots were not. The specimens were embedded with acrylic resin up to 3 mm from the coronal aspect, and the periodontal ligament was simulated. The 50 weakened roots were restored with (n=10) CPC-gold (cast post and core made of gold alloy), CPC-Ni (cast post and core made of Ni-Cr alloy), FP (glass fiber posts), FP-W (glass fiber posts with a wider coronal diameter), and FP-CR (fiber posts relined with composite resin). The 30 nonweakened roots were restored with (n=10) CPC-gold, CPC-Ni, and FP. All of the posts were adhesively cemented. All of the specimens were mechanically cycled (37°C, 45°, 130 N, 2.2 Hz, and 1.5 million pulses) and evaluated after every 5 × 10(4) cycles to evaluate the presence of cracks as a primary outcome (event). The specimens that survived cycling were subjected to a fracture load test (load application on the palatal aspect at a 45° inclination). Failure mode was classified as favorable (above the simulated bone level) and catastrophic (below the simulated bone level). Survival rates were estimated using the Kaplan-Meier method. Fracture load data were analyzed using the Kruskal-Wallis test (α=0.05) for weakened roots, one-way analysis of variance, and Tukey test (p<0.05) for non-weakened roots, and Student t-test (p<0.05) compared nonweakened vs weakened roots for the same post system.
For the preliminary survival results, FP-W showed a higher survival rate when compared with CPC (gold/Ni). For the fracture load (N), the statistical analysis (p<0.0001) presented differences among the weakened groups: CPC-gold (541.4) = CPC-Ni (642.6) > FP (282.2) = FP-W (274.1) = FP-RC (216.6). No differences were observed for the groups that were nonweakened (majority of favorable failures): CPC-gold (459.3) = CPC-Ni (422.0) = FP (347.9). Weakened roots restored with CPC-gold promoted high values of load fracture and unfavorable failure rates.
Cast post and cores or fiber posts can be used for restoring nonweakened roots. However, for weakened roots, a fiber post with a wider cervical emerging diameter appears to be a better alternative when compared with cast post and cores.
To evaluate the survival rate, success rate, load to fracture, and finite element analysis (FEA) of maxillary central incisors and canines restored using ceramic veneers and varying preparation ...designs.
Thirty human maxillary central incisors and 30 canines were allocated to the following four groups (n=15) based on the preparation design and type of tooth: Gr1 = central incisor with a conservative preparation; Gr2 = central incisor with a conventional preparation with palatal chamfer; Gr3 = canine with a conservative preparation; Gr4 = canine with a conventional preparation with palatal chamfer. Ceramic veneers (lithium disilicate) were fabricated and adhesively cemented (Variolink Veneer). The specimens were subjected to 4 × 10(6) mechanical cycles and evaluated at every 500,000 cycles to detect failures. Specimens that survived were subjected to a load to fracture test. Bidimensional models were modeled (Rhinoceros 4.0) and evaluated (MSC.Patrans 2005r2 and MSC.Marc 2005r2) on the basis of their maximum principal stress (MPS) values. Survival rate values were analyzed using the Kaplan-Meier test (α = 0.05) and load to fracture values were analyzed using the Student t-test (α = 0.05).
All groups showed 100% survival rates. The Student t-test did not show any difference between the groups for load to fracture. FEA showed higher MPS values in the specimens restored using veneers with conventional preparation design with palatal chamfer.
Preparation design did not affect the fracture load of canines and central incisors, but the veneers with conventional preparation design with palatal chamfer exhibited a tendency to generate higher MPS values.
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